Department of Medicine
Ph : (612) 624-6657
Room: 5-126 MCB (612) 624-6645
king@mail.ahc.umn.edu
Research Interests
There are two major areas of emphasis in Dr. King's laboratory: molecular basis of disease using the melanin pathway and human oculocutaneous albinism as a model system, and the identification of genes responsible for complex common diseases using automated linkage analysis and gene mapping techniques. Seven genes responsible for oculocutaneous albinism have been identified.
Mutations of the tyrosinase gene on chromosome 11q produce OCA1 or tyrosinase related OCA, and more than 100 mutations of this gene have been identified. Studies in Dr. King's lab address several aspects of this gene in OCA1. First, mutations associated with residual enzyme activity and the development of skin and hair pigment (OCA1B phenotype) are analyzed by site-directed mutagenesis and expression studies, to determine the effect of each mutation on enzyme processing and function, and the potential mechanism for the reduction in activity. Second, structure:function studies of the tyrosinase enzyme, using crystallography and three dimensional structural analysis of the protein, are underway in collaboration with the Structural Biochemistry group to determine the functional domains of the enzyme and to investigate how mutations alter enzyme function. Third, levels of tyrosinase gene transcription are being explored using ectopic expression in lymphoblastoid cell lines established from individuals with different types of OCA1, in an attempt to identify regulatory mutations in individuals who meet the clinical criteria for OCA1 yet have only one or no mutation in the coding region of the gene. Finally, long-range sequencing and single nucleotide polymorphisms around the tyrosinase gene are being used to identify haplotypes that may carry regulatory sequences that are associated with normal and abnormal levels of pigmentation.
Mutations of the P gene on chromosome 15q are responsible for OCA2 or tyrosinase positive OCA, the most common type of OCA in humans, and a large number of mutations of this gene have been identified. In Dr. King's lab, the phenotypic range of OCA2 is being characterized through the analysis of unusual families with OCA2, and the potential function of the P protein are being explored, in collaborations with Murray Brilliant, Ph.D., University of Arizona, and Vincent Hearing, Ph.D., NCI, NIH.
The most significant clinical problem in human albinism is the loss of visual acuity associated with deficient melanin in the developing eye and optic system. To address this problem, studies that use microarray technology are being designed with mice that contain an inducible tyrosinase transgene, with the goal of characterizing the effects of retinal pigment epithelium melanization on gene expression and ganglion cell proliferation.
The second major area of emphasis in Dr. King's laboratory involves the development of methods for mapping and identifying genes responsible for common complex diseases. Microsatellite markers that cover the genome are used in an automated system for rapid genotyping of individuals and families. The results of the DNA analysis flow directly to the linkage software and the pedigree programs. This technology is currently being used in a collaborative study of asthma (CSGA). A series of 30 or more large multiplex families have been evaluated and several potentially relevant chromosomal regions identified through sib-pair analysis. Linkage and disequilibrium analysis and fine point mapping have narrowed several potentially important regions on chromosome 1, 4 and 13, and candidate genes are being evaluated.
Recent Publications